1. Field of the Invention
The invention is related to the field of communications, and in particular, to telephone conference calls.
2. Description of the Prior Art
Telephone conference calls allow telephone conversations between three or more persons. A telephone conference call, or teleconference, is typically performed by a telephone system device called a bridge. The bridge joins together multiple participants to enable group communication. In order to join the teleconference, each participant is typically given a pre-assigned telephone number to call. In the prior art, the pre-assigned number is statically assigned to the teleconference before the teleconference actually occurs, and may be assigned days in advance. When the participant dials in, the telephone system receives the pre-assigned bridge telephone number and may ask the participant for a password or personal identification number (PIN). The participant is then connected to a corresponding conference bridge by a telephone system and may join a conference.
In the prior art, teleconference bridging is commonly performed through bridge facilities. Typically, such bridge facilities are located in various geographic areas, and can handle large numbers of incoming conference calls. Each bridge facility can contain multiple bridges and additionally can contain a routing device, including a Voice Response Unit (VRU) and processor. A call coming into the bridge facility is routed to a particular bridge in the bridge facility by the routing device.
However, the prior art static bridging approach has several drawbacks. Due to the popularity of telephone conferencing, many people may be participating at any time. If load changes occur, the bridge facility has to perform some manner of load balancing. Some examples of load changes are when participants drop out of a teleconference, when unexpected participants join a teleconference, when a technical problem occurs in any part of the bridging system, etc. The prior art attempts to avoid load balancing by under-utilizing bridges, i.e., each bridge in a bridge facility is typically not fully loaded. For example, each bridge in a prior art bridge facility is typically loaded to only about 60% of capacity in order to allow for unforeseen load changes.
FIG. 1 shows a telephone system performing a prior art load balancing. In this example, a first bridge facility 101 needs to transfer some conference call traffic to a second bridge facility 102. The prior art load balancing is accomplished by the first bridge facility 101 linking to the second bridge facility 102 and passing some conference calls to the second bridge facility 102. The circuits 103 from the callers to the first bridge facility 101 are maintained, and are linked to the second bridge facility 102 via additional telephone circuits 104, as shown. The prior art load balancing approach therefore ties up the additional circuits 104. In addition, the prior art load balancing approach occurs only after a traffic problem has occurred, and does not prevent loading problems. Geographic load balancing, wherein a bridge facility is selected according to the location of the caller and the bridge, is not achieved. Furthermore, the prior art requires computationally expensive VRU technology at a bridge facility. Moreover, the routing device and the VRU are unnecessarily duplicated in each bridge facility.